In general, there is a need for lithium-based, lithium-ion based, or similar electrochemical cells that exhibit high energy density over a large number of charge-discharge cycles. There are two basic approaches to achieve high energy density in such cells. The first involves providing high energy materials. The second involves using lightweight materials.
For example, the first approach may involve providing anode and cathode materials that exhibit a high electrochemical potential difference. This approach typically requires the use of an electrolyte containing lithium ions that is substantially electrochemically stable relative to both the anode and the cathode. This approach also typically involves the formation of an ionically conductive layer that allows for appropriate electrochemistry to take place without unwanted side reactions. Optionally, the electrolyte may be provided in the form of catholyte, a material that is considered both a cathode material and an electrolyte material.
As discussed above, the second approach to achieve high energy density involves providing lightweight electrode materials. Accordingly, the large free energy of the reaction between lithium metal and air has attracted the interest of battery researchers for decades. Both lithium metal and air are considered light-weight materials. At a nominal potential of about 3 volts, the theoretical specific energy for a Li/O2 battery in a non-aqueous electrolyte is over 11,000 Wh/kg for the reaction forming Li2O2. Such a battery would rival the energy density for hydrocarbon fuel cells. Some have suggested that rechargeable Li/Air cells and batteries could be commercially viable if lithium containing anodes were protected in a manner to ensure that moisture in air does not directly contact the lithium therein so as to avoid generating hydrogen gas in an uncontrolled manner.
In short, there is a need to provide novel and nonobvious materials to address the above-discussed technical problems. There is also a need to provide an electrochemical cell of an appropriate construction to meet the long-felt need for stable and high-performance electrochemical batteries that exhibit exceptional high energy density.